With "slightly more" than $18 million either pledged or in hand, the Kennedy Library Corporation has suspended fundraising activities until its architects draw up final plans and decide how much money they need.

James V. Lavin, director of the fund raising campaign, said yesterday that the architects, I.M. Pei and Associates, probably would not finish their work until October. "Then we'll decide whether to raise $22 million or leave the fund as it is," he said.

In the meantime, Lavin said he will keep in touch with foundations and foreign governments which might contribute the library it additional funds are needed. Sixty countries have expressed interest in the project and some have already made anonymous donations.

The bulk of the money has come from more than six million private donors, he said, Although no figures are available on the average size of the contributions, Lavin commented that "this is not one of those campaigns where 10 or 12 people give most of the money. We had support from millions of high school and college students."

Some $2.5 million came from foundations, with the Ford Foundation giving million towards the creation of the John F. Kennedy Institute of Politics, which will be part of the library complex but run by the Graduate School of Public Administration. The Kennedy family also made a "substantial" contribution, Lavin said.

The architects have been delayed by the shifts in the library site. President Kennedy had asked that his papers be placed in a library located at the Bennett Street MBTA Yards near Eliot St. It proved too difficult to purchase the land, however, and Harvard instead offered him some land near the Business School, which he accepted. After the assassination, plans were made to locate the memorial on the same site.

But last September a state commission recommended that the Commonwealth buy all 12 acres of their repair yards and code as many as are needed for the library to the government.

Since then, Pei has been working on the details of the library and the archives, which will be put under Federal supervision when they are completed, the Institute and commercial dwellings. Pei hopes that the commercial buildings such as restaurants and gift shops will help case the strain on Harvard Square that will be produced by an estimated 700,000 visitors per year to the library.

It will probably take the MBTA two years, Lavin said, to find a new site for its repair yards and move its equipment. It is estimated that the library complex will not be completed until the end of the decade, though certain programs related to it are already operating. Many of President Kennedy's friends and associates are having their impression of the New Frontier tape-recorded as part of a project in oral history, and next year the Institute of Politics will begin bringing together scholars and men experienced in politics.

The institute will probably be located in temporary offices in the Radcliffe Institute of Independent Studies on Mt. Auburn Street until the permanent buildings are completed, not before the end of the decade.